Polyunsaturated fatty acids (PUFAs) are considered to be useful for nutritional, pharmaceutical, and industrial applications, as well as other purposes. However, the current supply of PUFAs from natural sources (e.g., fish oils and algal oils) and from chemical synthesis is not sufficient or cost-effective for many long-term commercial needs.
Vegetable oils derived from plants (e.g., oil seed crops) are relatively inexpensive, do not have the contamination issues associated with fish oils, and are considered sustainable. However, the PUFAs found in commercially-developed plants and plant oils do not typically include more saturated or longer-chain PUFAs, and only typically include fatty acids such as linoleic acid (eighteen carbons with 2 double bonds, in the delta 9 and 12 positions—18:2 delta 9,12) and linolenic acid (18:3 delta 9,12,15).
The production of more unsaturated or longer-chain PUFAs in plants by the modification of the fatty acids endogenously produced by plants has been described. For example, the genetic modification of plants with various individual genes encoding fatty acid elongases and/or desaturases has been described as resulting in the generation of leaves or seeds containing significant levels of longer-chain and more unsaturated PUFAs, such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), but also containing significant levels of mixed shorter-chain and less unsaturated PUFAs. Qi et al. (2004) Nature Biotech. 22:739; PCT International Patent Publication No. WO 04/071467; Abbadi et al. (2004) Plant Cell 16:1; Napier and Sayanova (2005) Proc. Nutr. Soc. 64:387-93; Robert et al. (2005) Functional Plant Biol. 32:473-79; U.S. Patent Publication No. 2004/0172682; Petrie et al. (2012) PLOS One 7:e49165; and U.S. Provisional Application No. 61/345,537 (filed May 17, 2010).